1. Field of the Invention
This invention relates to a process for producing an L-amino acid. More particularly, it relates to a process for producing an L-amino acid from DL- and/or L-amino acid amide by action of an enzyme prepared by a specific microorganism.
L-amino acids are important compounds as food additives, feed additives, and intermediates of medicines and various industrial chemicals.
2. Description of the Prior Art
In general, L-amino acids are produced by formentation or by optical resolution of DL-amino acids prepared in an organic synthetic-chemical method. Recently, there have been proposed and made practicable a large number of so-called chemico-enzymatic processes which comprise converting precursors inexpensively obtainable by chemical synthesis into L-amino acids by using enzymes.
Typical examples of the chemico-enzymatic processes for producing L-amino acids include, for example, a process comprising acting acylase produced by a microorganism on an N-acyl derivative of DL-amino acid (Japanese Patent Publication No. 22380/66), a process comprising acting hydantoinase produced by a microorganism on a hydantoin-substituted DL-amino acid derivative (Japanese Patent Publication No. 2274/79), a process comprising acting aspartase produced by a microorganism on fumaric acid (Japanese Patent Publication No. 18867/82 and Japanese Patent Application Kokai (Laid-Open) No. 140890/84), and a process comprising acting phenylalanine ammonia lyase produced by a microorganism on cinnamic acid (Appl. Environ, Microbiol. 42, 773 (1981)).
However, these processes involves problems, for example, complicated reaction systems, severe reaction conditions and expensive starting materials, and can stand improvement as industrial production processes.
Recently, there have also been proposed processes comprising reactions for producing various L-amino acids from the corresponding DL- or L-amino acid amides by using enzymes produced by microorganisms, for example, a process using an enzyme L-amidase produced by microorganisms belonging to Bacillus, Bacteridium, Micrococcus and Brevibacterium (publicized in Japanese Official Patent Gazette No. 500319/81) and a process using L-amidase produced by various yeasts and bacteria (Japanese Patent Application Kokai (Laid-Open) Nos. 13000/82, 159789/84 and 36446/85).
However, all of these processes involve a problem of low L-amidase activity, and they are experiment examples in which production reactions of L-amino acid were carried out by using a large amount of cells, or nothing but a finding that well-known strains belonging to various genera hydrolyze various DL- or L-amino acid amides to give the corresponding L-amino acids. Because of use of these microorganisms, they cannot possibly become economically advantageous production processes from the viewpoint of industrial processes for producing L-amino acids from DL- or L-amino acid amides by action of enzymes produced by microorganisms.